(CNN) -- Aaron Hernandez was destined to be a football superstar and was already one of the NFL's most promising tight ends.

But less than a year after signing a $40 million contract extension with the football powerhouse New England Patriots, he was charged with first-degree murder.

Two hours after his arrest on June 26, 2013, the Patriots dropped him from the team.

Hernandez, then 23, pleaded not guilty in the slaying of Odin Lloyd and is being held in a Massachusetts jail without bail. Hernandez has also been charged in the slayings of two other men, and some of his closest associates are facing serious charges in connection with the alleged crimes.

Friends and fans alike wonder: How could the star player who had more than 900 receiving yards in 2011 now be accused of murdering three people?

From 'golden boy' to behind bars

Long before Hernandez made national headlines, he was a standout athlete in Bristol, Connecticut, who came from a family described as a local sports dynasty.

"I don't think there was another family that was more familiar in Bristol," Bob Montgomery, who covers high school sports for the Bristol Press, told CNN.

The young Hernandez was the "golden boy," playing football, basketball and running track, following in the footsteps of his uncle, older brother and father -- all well-known athletes in the community.

Hernandez's father constantly pushed his son, requiring him to practice for hours before he could go out with friends.

"I saw a closeness with them that I'd never seen before," Montgomery said of the relationship between Hernandez and his father.

But his father, the man who kept the 16-year-old anchored, died from complications after a routine surgery.

Hernandez left high school halfway through his senior year in January 2007 to join the University of Florida Gators, and trouble seemed to follow.

In just his first semester, a police report says Hernandez got into a fight at an off-campus restaurant, sucker-punching the manager and rupturing his eardrum.

The following fall, there was a shooting near a local club. Police reports link Hernandez and several other University of Florida football players to an argument in the parking lot.

Hernandez was one of more than 20 people interviewed by police, and he was the only one who did not make a statement after invoking his right to counsel.

At the time, Hernandez's mother told the Orlando Sentinel newspaper, "I know he was at the club, but he never saw any shooting."

The case remains open, and no one has been charged.

Hernandez was also suspended at least once for marijuana, an issue that would follow him as he entered the draft his junior year.

Trying to put the alleged drug use behind him, Hernandez wrote a letter to the Patriots' director of personnel.

"If you draft me as a member of the New England Patriots, I will willfully submit to a bi-weekly drug test throughout my rookie season. ... In addition, I will tie any guaranteed portion of my 2010 compensation to these drug tests and reimburse the team a pro-rata amount for any failed drug test," he wrote, according to the Boston Globe.

Before the draft, Hernandez was expected to be a first or second round pick. He was passed over until the fourth round, when the Patriots selected him.

By the end of the second season, he was a bona fide star, inking the five-year contract extension worth $40 million.

One month before signing the deal, however, he was partying at a Boston club. That same night, two men from the club were found dead.

District Attorney Patrick Haggan described the scene in a Massachusetts courtroom in May, saying Hernandez became "angered and increasingly agitated, particularly after Mr. Abreu smiled and did not apologize."

Hernandez's friend tried to calm him down, and the pair walked outside and eventually entered a second club across the street, the prosecutor said. Court documents identify that friend as Alexander Bradley, who would go on to accuse Hernandez of shooting him in the eye in an incident that would take place seven months later.

After leaving the second nightclub, Hernandez and the friend returned to their SUV and pulled over on a nearby street where Hernandez removed a revolver from the engine block, Haggan said.

Hernandez began trailing Abreu, Furtado and three of their friends in his SUV, authorities said.

He then pulled up to the victims' car at a red light and leaned out the driver's side window with a loaded revolver, Haggan told the court.

Hernandez allegedly said, "Yo, what's up now," followed by a racial slur, and fired at least five rounds from a .38-caliber revolver, Haggan said.

Abreu, the driver, was shot several times and fatally hit in the chest. Furtado was sitting in the front passenger seat and suffered multiple gunshot wounds, including one to the head, Haggan said.

Hernandez was charged in the double homicide just last month, and he pleaded not guilty. Investigators found evidence they believe links him to the 2012 slayings while investigating an entirely different case -- the slaying of Odin Lloyd.

The killing of Odin Lloyd

In the early hours of June 17, 2013, Lloyd was shot seven times. The semi-pro football player's body was found by a jogger the next afternoon in an industrial park in North Attleboro, Massachusetts.

Lloyd, who was dating the sister of Hernandez's fiancee, had been partying with Hernandez just before his death, his friends told CNN.

Prosecutors say Lloyd was last seen with Hernandez and Hernandez's two associates, Carlos Ortiz and Ernest Wallace, around 2:30 a.m. in a rented silver Nissan Altima.

Surveillance video from security cameras at an industrial park showed an Altima heading toward a secluded area at 3:22 a.m.

At the same time, chilling text messages from Lloyd's phone were sent to his sister telling her he was with "Nfl," adding, "just so u know."

Between 3:23 and 3:27 a.m., workers nearby reported hearing gunshots. At 3:29, a camera showed an Altima pulling into Hernandez's driveway, about a half a mile from the death scene.

Three people got out of the car, and Lloyd was not one of them.

Nine days later, Hernandez was arrested and charged with first-degree murder and other weapon-related charges. He has pleaded not guilty.

Investigators believe Hernandez's simmering anger over two incidents at a nightclub and his apartment led him to allegedly kill Lloyd two nights later, CNN has learned.

One of the incidents involved Lloyd seeing guns and ammunition stored at Hernandez' so-called flop house, his apartment in Franklin, Massachusetts. The other thing that set off Hernandez was a conversation Lloyd had with two men at a club earlier that night, June 14, 2013, a source tells CNN.

The cumulative effect apparently reached a breaking point for reasons that most people would find inconsequential. The source would not say what that was, but compared it to something as insignificant as the spilled drink that allegedly led to the 2012 Boston double slaying.

Lloyd's killing did not involve possible knowledge of that double slaying as investigators previously considered, the source added.

In April, Ortiz and Wallace were also charged in Lloyd's slaying. They, too, have pleaded not guilty.

Life in a jail cell

Today, Hernandez is behind bars in a 7-by-10 foot cell. Sheriff Thomas Hodgson, who runs the jail where Hernandez is incarcerated, says he has talked to inmate No. 174954 at length.

Hernandez, Hodgson says, spends his time reading the Bible and another book he suggested, "Tuesdays With Morrie."

Hodgson has encouraged Hernandez to turn to his childhood anchor, his late father. The father-son relationship has come up in their conversations and could have played a role in his checkered past.

"His dad clearly kept him grounded," Hodgson said. "When you lose that person and there's no one there to help you process it in a healthy way, at 16 you're going to reach out to anybody that's older than you to deal with it."

Even behind bars, Hernandez has found trouble. He has been accused of getting into a physical altercation with another inmate and is facing charges of assault and threatening a guard's life.

That's on top of three murder charges, the lawsuit claiming he shot his friend in the face and three civil suits from the families of his alleged victims, among other things.

As for the Lloyd case, Hernandez's lawyers contend the circumstantial evidence is full of gaps.

"There's certainly a lot of what I would call smoke. There's no doubt about it," defense lawyer Jamie Sultan said during a June 16 hearing. "But that's not probable cause that he committed murder. And you can't just throw a bunch of stuff against the wall and say that's good enough."

No murder weapon has been found, and while at one point it seemed likely that Ortiz would be a key witness against Hernandez, there are now serious questions about his credibility.

And the text Lloyd sent to his sister? The jury may never hear about it.

"I expect the defense to say that this is hearsay," legal analyst David Frank said.

Hernandez's lawyers and mother declined to be interviewed, but both predict he will be cleared. It's a possibility that haunts Lloyd's loved ones.